An electric lighting apparatus for a bicycle This invention relates to an electric lighting apparatus for a bicycle, the apparatus comprising a dynamo connected by a time lag section to a relay control circuit which includes transistors, a release circuit containing a capacitor, and a relay which connects a lamp circuit alternately to the dynamo and to an auxiliary voltage source, for example a battery.
Such an arrangement is disclosed in German Specification No. 24 27 740. In this arrangement, the auxiliary source is connected into the lamp circuit when the dynamo output voltage falls below a certain minimum value. However, it may happen that within a certain range of dynamo speeds, the relay continually switches from one of two states to the other, i.e. between the state in which it connects the auxiliary source to the lamp circuit and the state in which it connects the dynamo to the lamp circuit.
In such circumstances, the bicycle lamp flickers, which is undesirable.
It is an object of this invention to provide an electric lighting apparatus in which the unstable state of the relay is substantially avoided.
According to this invention an electric lighting apparatus for a bicycle comprises a dynamo connected by a time lag section to a relay control circuit which includes transistors, a release circuit having a capacitor, and a relay which connects a lamp circuit alternately to the dynamo and to an auxiliary voltage source, wherein the relay has an additional switching contact operable to form a connection between the dynamo and earth. A preferred feature of the apparatus is the inclusion of a diode in a parallel with the release circuit capacitor for protection of the latter against destruction due to any excessively high negative voltage peaks generated by the dynamo.
In addition, a resistor may be connected between the dynamo output and earth, this resistor forming part of a voltage divider, thereby preventing excessively rapid discharge of the auxiliary voltage source when the dynamo is not connected, as for example when the bicycle is in storage.
The invention will now be described by way of example with reference to the drawing, which is a circuit diagram of an electric lighting apparatus for a bicycle in accordance with the invention.
The apparatus comprises a dynamo G which is connected to a relay control circuit by way of a diode D1, said control circuit formed by transistors T1, T2, T3. In addition, dynamo G is connected to the relay control circuit through a diode D2 and a time lag section consisting of resistors R1, R2 and a capacitor C1. C1 is connected between the junction of R1 and R2 on one side and earth on the other. The release circuit includes a capacitor C2 which is connected between the base and the emitter of the transistor T2 of the relay control circuit. A resistor R4 is connected between the base of the transistor T2 and the connection between an auxiliary voltage source in the form of a battery B and the emitter of the PNP transistor T3. Transistor T2 collector is connected to the base of transistor T3 through a resistor R5.A relay R is situated between the collector of the transistor T3 and earth; a diode D4 is connected in parallel with the relay R. The relay has a switch contact S1b which is normally connected to the lamp circuit L containing the lamps L1, L2, and thereby connects the circuit L to the output of the dynamo G. In accordance with the invention, a further
the output of the dynamo G and earth. This switch contact is connected in series with a resistor R6. In the normal state and when the lamp circuit L is supplied by the dynamo G, the switch contact Sia is open, as shown in the Figure. Parallel with the circuit consisting of switch contact S1a and resistor R6 is a resistor R7 and function of which will be described below.
As shown in the Figure, the diode D1 is connected by its cathode to the output of the dynamo G, while the diode D2 is connected by its anode to the connection between the output of the dynamo G and the relay switch contact S1a or one of the connections of resistor R7. The anode of diode D1 is connected by way of resistor R3 to the connection of the cathode of a diode D3 which is connected in parallel with the capacitor C2 and connected by its anode to the emitter of transistor T2. The cathode of diode D4 is connected to the collector of transistor T3 while the anode of D4 is connected to earth.
The resistance value of resistor R1 is preferably 470 Q, that of R2,100 k Q and that of R3, 200 Q. The value of resistor R4 is 1 M Q, that of R5 is 4.7 k Q, that of the series resistor R6 to the switch contact Sia is 4.7 and that of resistor R7 is 75 k Q. The values of capacitors C1 and C2 are 220 \if and 3.3. \iF respectively.
The lighting apparatus described above operates as follows:- When the dynamo is connected and the bicycle is slowly started, the relay R is initially de-energised.
The capacitor C1 is discharged, and the current path through T1, T2, T3 is blocked. When the dynamo voltage rises above the threshold voltage of diode D2 and transistor T1, i.e. above about IV, the capacitor C1 begins to charge and transistor T1 becomes conductive. Transistor T2 also becomes conductive since the base of transistor T2 becomes more positive in relation to the emitter by way of the resistor R4. The relay R is energised and the lamps L are connected to the auxiliary voltage source B by way of the relay contact S1b. At the same time, the relay contact S1a closes, which relay contact definitively loads the dynamo G by way of R6. If this loading of the dynamo through resistor R6 did not occur, the unloaded dynamo voltage would suddenly rise and cause the relay to drop out.
The switching over of the relay contact S1b to dynamo operation would again produce an alteration in loading, which would again cause energising ofthe relay R, which would bring about repeated switching of the relay. A stable switching state of relay R therefore could not be established. This stable switching state is established in accordance with the invention by the relay contact Sia and the resistor R6, as follows: if the dynamo voltage continues to rise to a value above 2V, the base of transistor T2 becomes more negative byway of D1, R3, and the voltage falls below the threshold voltage of transistor T2, so that the latter is turned off.
Transistor T3 is thereby also turned off. Relay R drops out. The lamps L are again connected to the dynamo G, and the relay contact Sia again switches off the resistor R6. The lamp is now supplied with current by the dynamo.
If the dynamo voltage decreases due to deceleration and falls below 1.5V, the base potential of transistor T2 in relation to the emitter again increases and the threshold value ofT2 is exceeded, so that transistor T2 again becomes conductive, and transistor T3 is thereby also rendered conductive, the relay R is attracted, and the lamps L are connected to the auxiliary voltage source B by way of the relay contact S1b. The lighting is now supplied through the auxiliary voltage source B.
If the velocity is further reduced and the dynamo voltage falls to zero, then capacitor C1 is no longer charged through D2, R1 and is discharged by way of R2, RBE of T1. After expiry of the time constants of 2 to 3 minutes, the capacitor C1 is discharged. The transistorT1 is non-conducting, with the result that transistor T3 is also non-conducting. The relay R drops and the circuit returns to its original state.
Diode D3 limits the emitter-base voltage of transistor T2 to 0.7V and protects it against voltage breakdown. The capacitor C2 serves to smooth out the negative voltage half waves travelling from the dynamo by way of D1, R3.
Resistor R7 and resistor R4togetherform a voltage divider. The special choice of these resistors ensures that when a fuctional auxiliary voltage source B is installed and the connection for the dynamo G is not switched on, for example during storage, the relay R will not periodically be energised and de-energised. Resistor R7 cooperates with resistor R4 to divide the battery voltage so that capacitor C1 cannot be charged up by the auxiliary voltage source B. The quiescent current is consequently about 30 Ȧ, so that the auxiliary voltage source B cannot become discharged before 33,000 hours at the earliest.